Question: $400$ is what percent of $1000$ ?
Answer: Having a percent of something means that you get that percent out of every $100$ We can set up a proportion to find out what percent of $1000$ we need to take to get $400$ $ \dfrac{{\text{percent}}}{100} = \dfrac{{\text{part}}}{{\text{whole}}}$ Which things do we know, and what are we trying to find? We are trying to find the ${\text{percent}}$ . Is $1000$ the ${\text{part}}$ or the ${\text{whole}}$ The $1000$ is the ${\text{whole}}$ . This means the ${\text{part}}$ is $400$ $ \dfrac{{\text{percent}}}{100} = \dfrac{{400}}{{1000}}$ If we divide the denominator of the fraction on the right by $10$ , it will be the same denominator of the fraction on the left. To keep things equal, let's also divide the numerator on the right by $10$ $ \dfrac{{\text{percent}}}{100 } = \dfrac{{400 \div 10}}{{1000 \div 10}}$ $ \dfrac{{\text{percent}}}{100 } = \dfrac{{40}}{{100}}$ $ {\text{percent}} = {40}$ So $400$ is $40\%$ of $1000$.